Sensor and Controller Catalog

Thermocouples

TRUE SURFACE (TST)

Increase Surface Temperature Accuracy with Improved Thermocouple Design Watlow’s TRUE SURFACE thermocouple (TST) offers superior accuracy for measuring flat surface temperatures. This compact, highly accurate sensor isolates the thermocouple junction from ambient airflow. The TST typically achieves accuracy and repeatability between one to two percent (∆T). The TST, with its removable molded cover, fits into corners and other tight locations. TSTs are easy to install with a variety of commonly used screw types. Watlow’s TST sensor is ideal for many applications including semiconductor chambers, platens, packaging, cleaning and food preparation. Features and Benefits Isothermal measuring junction • Offers excellent thermal conductivity for the measuring junction Molded insulator • Isolates the isothermal measuring block from ambient airflow Compact, universal package • Fits into corners and other tight locations easily (0.44 in. (11.88 mm) side by 0.24 in. (6.10 mm) high) • Molded insulator is removable for applications where an even smaller package is needed Temperature rating of 400°F (200°C) • Offers superior application flexibility for a wide variety of surfaces Options • Ungrounded or grounded junction(s) • Type J or K calibrations • Shielded lead wire with drain, either isolated from or connected to the sensor sheath

Steady State Temperature Measurement Test

• Purpose: To determine and compare the steady state error of the Watlow TST and a common “washer”-style thermocouple at several temperature settings with and without ambient airflow. • Test Description: Each sensor was attached to a brass hot plate and allowed to reach equilibrium before temperature readings were taken. Room temperature air was then blown onto the hot plate and the sensors. Temperature readings were taken after the system reached the new equilibrium point. The test was performed with a 20, 40, 60 and 80°C differential between the hot plate temperature and ambient. • Results: Ambient temperature = 25°C.

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